1. Field of the Invention
The present invention relates to a method of manufacturing a recording medium and a recording medium and, in particular, to a method of manufacturing a recording medium into which still image information is recorded by magnetic, optical and optical-magnetic recording/reproducing apparatus or from which recorded image information is reproduced by the same recording/reproducing apparatus, and a recording medium.
2. Description of the Related Art
Recently, there has been developed an attractive electronic still camera system in which an image pickup device such as a solid image pickup element, an image pickup tube or the like is combined with a recording device using an inexpensive magnetic disc having a comparatively large memory capacity to still photograph an object electronically and record the still-photographed image of the object into a rotating magnetic disc, with the recorded still image being reproduced by a separate television system or printer.
In the above-mentioned electronic still camera system, the magnetic disc is generally used in the form of a magnetic recording cartridge. The magnetic disc cartridge contains therein a magnetic disc which is rotatable and is capable of magnetically recording therein still image information and the like. For actual use, the magnetic recording cartridge is mounted to a magnetic recording device which is contained in an electronic camera or to a reproducing device which is arranged integrally with the magnetic recording device or separately therefrom. In mounting the magnetic recording cartridge to the magnetic recording device or reproducing device disposed within the electronic camera, it is troublesome and inconvenient to place a center hole, which is formed in a center core disposed in the central portion of the magnetic disc within the magnetic recording cartridge, directly over a rotary drive shaft provided on the side of the magnetic recording or reproducing device. Thus, there is a possibility that the magnetic recording cartridge cannot be mounted properly to the magnetic recording or reproducing device.
In order to eliminate the above-mentioned trouble, conventionally, there has been proposed a device for loading or unloading the magnetic recording cartridge. The conventional magnetic recording cartridge loading/unloading device comprises an upper cover pivotally supported on a main body of a magnetic recording or reproducing device, and a holder which can be formed integrally with the upper cover or which can be pivotally supported on the device main body or on the upper cover. In the magnetic cartridge loading/unloading device, the magnetic recording cartridge including therein a magnetic disc is inserted into the holder and after then the upper cover is closed to thereby mount the magnetic disc within the magnetic recording cartridge onto a rotary drive shaft of the main body of the magnetic recording/reproducing device. There is disposed a center core in the central portion of the magnetic disc and the rotary drive shaft can be fitted into the center hole formed in the center core to rotate the magnetic disc contained within the magnetic recording cartridge.
Here, it should be noted that the center core of the magnetic disc must be accurately mounted onto the rotary drive shaft. If such mounting is insufficient, then the magnetic disc will be rotated in an offset manner or irregularly, which will incur a possibility that the magnetic head may not be able to record signals into the magnetic disc or reproduce the same from the magnetic disc in an accurate manner as well as a possibility that such offset or irregular rotation of the magnetic disc can have ill effects on the magnetic disc, magnetic head and the like. In view of this, according to the center core of the magnetic disc according to the prior art, in the center hole in the center core into which the drive shaft is fitted, there is provided a resilient piece member formed of resin material. That is, the center core can be pushed against the drive shaft with a given pressure and can be accurately mounted to the drive shaft by means of the energization force of the resilient piece member.
However, the above-mentioned resilient piece member of resin material is low in durability and thermal resistance and thus it may be deformed plastically, so that the magnetic disc may be mis-centered and then it may be rotated eccentrically. In order to solve this problem, in Publication of Laid-open Japanese Utility Model Application (Jikkai) No. 59-138063, there is proposed a center core which uses a metal plate spring in place of the resin resilient piece member. The metal plate spring is adapted such that the two ends thereof are supported in slits formed in the center hole in the center core into which the rotary drive shaft of the magnetic recording/reproducing device is inserted, and that the rotary drive shaft inserted into the center hole can be energized by the plate spring and thus can be pushed against the opposed surface thereof. However, due to the fact that the metal plate spring is simply disposed in the slits formed in the center hole in the center core, when the magnetic disc is fixed to the center core and an upper core for holding the plate spring is not provided, there is a possibility that the metal plate spring can get out of place owing to slight vibrations and the like during its assembling process.
Also, if the metal plate spring is pressed into or bonded to the slits in order to prevent the plate spring from dropping off out of place during the assembling process, then the forces of the metal plate spring may vary in intensity, making it difficult to chuck the recording disc to the rotary drive shaft of the magnetic recording/reproducing device.